In a wireless communication system such as an intervehicle communication system that carries out direct communication among wireless communication apparatuses without communicating by way of a wireless base station, communication conditions are assumed to change minute to minute with the movement of wireless communication apparatuses, with communication partners within the range in which communication is possible (communication range) being absent or few in number, or partners that can communicate becoming extremely numerous due to the dense concentration of communication apparatuses within a predetermined area.
Of these conditions, a condition in which wireless communication apparatuses are crowded together raises the problem that communication between wireless communication apparatuses increases, leading to congestion and a decrease in throughput. To deal with this type of problem, a method is proposed in Patent Document 1 in which congestion and the reduction of throughput is mitigated while ensuring wireless links with relatively close wireless communication apparatuses by controlling the transmission power to adjust the size of the communication range and thus limit the number of wireless communication apparatuses that are communication partners.
In the method disclosed in the above-described Patent Document 1, when a particular wireless communication apparatus decreases transmission power to decrease the communication range, the congestion of wireless communication is mitigated for other wireless communication apparatuses that are present outside the communication range because they become unable to detect wireless signals transmitted from the wireless communication apparatus that has decreased transmission power.
Nevertheless, in a wireless communication apparatus that has decreased transmission power, wireless signals that are transmitted from wireless communication apparatuses that are outside the communication range and that have not decreased transmission power are still detected as before, and the advantage derived from easing the congestion of wireless communication (enabling a mitigation of congestion and decrease of throughput) therefore cannot be obtained in the wireless communication apparatus.